A submersible pump especially for use in deep wells, either water or oil, comprises an electric motor and a plurality of pump stages, the motor being lowermost and separated from the pump stages by a seal section to substantially prevent well fluid leakage into the motor housing. At times there are a hundred or more pump stages and the electric motor may be some thirty feet in length with a diameter of approximately six inches. In order to change the pumping performance, pump stages can be added or subtracted from the assembly, generally requiring pulling the assembly from the well. This is not only time consuming and costly but is also inconvenient.